How to check if a directory exists? How to check if a command succeeds or failed? How to do string comparison and check if a string equals to a value? How to check if a string is in an array? How to use the Bash ternary operator? How to negate an if condition in a Bash if sta...
If you wanttomatchacharacterthat’s specialtothe regular expression grammar, it hastobe quotedtoremove its special meaning. This means thatinthepattern‘xxx.txt’, the ‘.’matchesanycharacterinthe string (its usual regular expression meaning), butinthepattern‘"xxx.txt"’ it canonlymatcha litera...
if [ ! -z err−o!−eapk ]; then 会报出-e无法找到的错误; 而if [ ! -z err]||[!−eapk ]; then 没问题; 整数比较 : -eq 等于,如:if [ "a"−eq"b" ] -ne 不等于,如:if [ "a"−ne"b" ] -gt 大于,如:if [ "a"−gt"b" ] -ge 大于等于,如:if [ "a"−ge...
Thesebinarylogical expressions compare two values, but there are alsounarylogical expressions that only look at one value. For example, you can test whether or not a file exists using the-elogical flag. Let’s take a look at this flag in action: cd~/Code[[-emath.sh]]&&echot||echof #...
# login shell will execute thisif[-n"$BASH_VERSION"];then# include .bashrc if it existsif[-f"$HOME/.bashrc"];then."$HOME/.bashrc"fifi 就是避免登陆时~/.bashrc被跳过的情况。 所以当系统里同时存在~/.bash_profile和~/.bashrc的时候,你如果把一些 alias 的配置写到了.bash_profile里,你就会发...
alias Used to define an alias for a specific command. bg Run a job in background mode. bind Used to bind a keyboard sequence. break Used to exit from a running loop in script. cd Change the directory to another directory. command Run a specific command without the normal shell lookup. ...
sysctl: Treat -f as alias for -p/--load (76549bb) xrandr: match the output name exactly for --mode (3556fcb) chmod: Fix "-" completion (a269a60) _xspecs: Simplify bash version check (ec630f5) test: Remove some no longer used old test suite code (a492414) tshark: Support prefer...
5 echo "Password file exists." 6 fi注意:使用[[]],而不是[],能够阻止脚本中的许多逻辑错误.比如,尽管在[]中将给出一个错误, 但是&&,||,<>操作还是能够工作在一个[[]]test之中.注意:在if后边,test命令和[]或[[]]都不是必须的.如下:
The exit status of a function definition is zero (success) unless another read-only function with a similar name already exists or a syntax error occurs. How to define and use functions in Bash? You can define functions in your .bashrc file with your other bash alias. In a shell script,...
#ifrunning bashif[ -n"$BASH_VERSION"];then# include .bashrcifit existsif[ -f"$HOME/.bashrc"];then."$HOME/.bashrc"fifi# set PATH so it includes user's private bin directoriesPATH="$HOME/bin:$HOME/.local/bin:$PATH" 1. 2.